Compensating apparatus for pantographs



J. H. LARRABEE COMPENSATING APPARATUS FOR PANTOGRAPHS Dec. 18, 1928.

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Filed Nov. 3, 1924 I I l I l I I 4 I l 1 1 l I l u I John H. Larrabee Attorney Dec. 1 8, 1928.

J. H. LARRABEE GOMPENSATING APPARATUS FOR PAN'I'OGRAPHS Filed Nov. 5; 1924 2 Sheets -Sheet 2 In ventm':

John H. Larrabee Attorney Patented Dec. 18,1928.

1 UNITED STAT JOHN H. LARRABEE, or wnsrrmeron, DISTRICT orcoLUMB'rA.

ooMrENsA'rIne APPARATUS ronrnnroennrns.

Application filed. November My invention relates to a compensating device foruse with any pantograph and has for an object the reproduction of charts, designs, drawings or diagrams with great accuracy. Y

Another object of my invention is to provide a device that will give a true reproduction even when the chart or other work to be copied, is distorted A further object is to provide a meansfor increasing the efiicicncy and reducing the cost of such work; V lVith these and other objects in view, my invention consists in the combination, construction and arangeinent otparts as will be hereinafter fully described. 1

Reference is to be had to the accompany ing drawings forming part of this specification in which like reference characters indicate corresponding parts throughout the several views, and in whichl igure 1 is a plan view of my invention. Figure 2 is a.

cross section on-the line 2 201 Figure 1. Figure 8 is across section on the line 3-3 of Figure 1. Figure 4 is a cross section on the line 44 of Figure 1. 1

\Vith particular reference to morals -1, 2, 3 and 4 represent the arms of any pantograph as used in reproducing deducingpointof the particular pantograph used to describe my invention. 8 1s a copy board upon which the Work to be reproduced is secured. Copy board -8is mounted on bearings 9 (Fig. 4) which are preferably. of the ball type, and slide on the surface of the metal. bed 10. In this. particular embodiment of my invention,- the movement of copy board 8 is confined to onedirection by means of rail 11, which is rigidly attached to the metal bed 10, and bearings 12 rigidly attached to the under side of the copy board 8 and sliding on the respective sides of rail 11.

An arm 13 is pivoted to arm 1 at15.v An

arm 14 is pivoted to arm 3 at 16. Arms 13, 14 and the compensating bar 18 arepivote-d together at point 17. The arms 13 and 14 are so proportioned and located in relation to arms 1 and 3 that they form an auxiliary pantograph with an anchor point in commen with the anchor point 5 of the larger pantograph, thus providing for a movement of the point 17 in the same direction and proportional to any movement of the tracing point 6. 1

Figure 1 nudrawings or diagrams. 5 is the'anchor point, 6the tracing point and 7 the-repro "3, 1924. Serial 110.741617.

As shown in Figure 8, the compensating erably recessed, the axis of which extended passes through POlll't 17. Passing through ar is positioned between the slotted rails, 19. Compensating bar 18 has a slot 20 pretthe slot 21 oi rails 19 and through the slot 7 20 of compensating bar 18 is a pivot 22, the lower portion oi which freely slides in the slot of the lower rail. 19 andthe upper portion of which is threaded to carry nut 23.

By adjusting nut 23 pivot 22- is madeto rigidiy engage the compensating bar 18-by means'oi the extended portion 24 of the pivot 22 and the sleeve 25 siidable about pivot .22 and in the 310501 upperjrail 19. The rails 19- are rigidlySUPPOI'tQCl' by brackets 26 which in turn are'securely fastened to the table 27. Ealotted rails 119 are in a position parallel to the twoopposite sides of the copy board 8. Compensating bar 18 is -joined to copyboard 8 by an adjustable con nectingrod 28. Rod28 is movably'connected to bar 18 ELUQQ. and to copy board 8" at 30. The whole apparatus is preferably mounted onatable 27. 'i The apparatus as above described operates in the following manner: i

The sides of the copy board Sare marked North, South,-Fiast and West for convenience in explanation- A copperplate 31 or other medium upon which the reproduction-is, to be pantographed is placed under the reproducing point 7 for all movements of thetracing point 6, the reproducing point 7 will move over the copper plate in the same direction and through distancesproportional to the movements of tracingpoint (3 in a North-South direction on a desired scale but distances in an East estdirection traced by the tracing point 6 will then be reproduced in a different scale and shorter in proportion to the shrinkage in the chart being traced.

If, however, when the tracing point 6 is It will'be readily seen that v inoving' in an East-IVest direction the copy board can he made to inove progressively under the tracing point in the seine direction and in an "amount equal to the shrinkage in the chart, then the reproducing point 7 Will reproduce East-"West distances traversed by the tracing point Ginccrrect proportion to the true dimensions of the chart and the effect etshr nkage Will be eliminated. The accomplishment of the required progress ve movement of the copy hoard under the tracing point as the tracing; point is inpved in an Ezist-i i est direction is a feature or m invention,

T hen the tracing point 6 is nioved in a "th South direction the center of the joint 17 nioxt'es in a North-South direction gniitthe pivot slides in the siotted rail 19 in a North-South direction and there is no, East-Vest movement of the connecting rod 28. A Hence the copy heard 8 remains 1 stationary.

When the tracing point6 nioves in an East-Test dlrection the center ot the -o1nt l7 noves in an East-W'Test direction, the

compensating bar, 18 pi vots about point and an East-West ,n oveinent communicated to thecfonnecting rod 28 and thence to the copy board 8. 'lhis inovenient of the copy board is proportional to "the Eastlw est movenient of the tracingpoint 6 and in a ratio depending upon the distance of the pivot 22 from the connecting rod-28. 7

NVhen th pivot point is South of the connecting red the copy board Sandjtracing pointG will noove in the sanie direction thus compensating for shrinkageand when the pivot 22-i'sNorth ofthe coi'inecting rod 28the copyho ard 8; and the tracing point 6 will move inopposite directions thus coInpensating for expani on), i

lVhen the pivot point 22 is on ,a line with the connecting rod 28 the copy board 8 will remain'stationary for all movements of the tracing point 6. This 'is the position of pivot point 22 for use When no distortion is to be compensated.

In operating the. pantograph with my con' pensating device, the amount of shrinkageorj; ansion to be compensator for must be determined and the pivot point 22 setaccordingly Settings of thefpivot point 22 necessaryto produce various percentages of compensation may: be computed and graduated on the compensating bar in any convenient scale.

It will be understoodjthat the above des'cription'and accompanying drawings coinint-erccnnec ed arins'and copy hoard for iniparting a j'n'ogressive inovoincnt to the copyboard in response tO IHOVGIDGHtof the tracing point thercover. v I

2. A parallelogram type pantograph copying arrangement 7 compris ng pairs ot interconnected arms, an anchor stern, one

pair heingpivcted to the anchor and another pa rcarrylng a tracing point and a reproducing point, ZLJlllQVitlJlG copyboard and ineans including an aux liary pantograph attached to said iste n and said first named arms for imparting 1 a progressive movement to the copy-hoard in response to movement of the tracing point thereover.

3, A. parailelogranr type pantograph copying; arrangement comprising pairs of interconnected arms, an anchor ste n, one pair"heing pivoted to thek nch or stern and another pair carrying a tracing poi ntand a reproducing point, an auxiliary ;-pantograph attached to said stem and said first a ned arms, a movable copy-board and means connected between the. auxiliary' pantograph and copy-hoard whereby a progressive movement is imparted to, the latter in response to movement of the tra'cingfpoint thereover said means including interconnected members, one of which is pivotally mounted;

41. A parallelogram type pantograph copying arrangement comprising interconnected arms, a tracing point carried by one of said arms, a reproducing point movable.

with the tracing point positionedonanother of said arms, a movable copy-hoard over which the tracing point is operable, and ineansconnccted to the interconnected 211113 and "copy board for moving the latter to compensate 1nthe reproduced copy for dimensional. variations in the copy to be traced.

OHN 'H. LA-RRA BEE. 

